As an ice making machine automatically producing ice blocks, a flow-down type ice making machine is known in which an ice making unit is configured with an ice making portion in which a pair of ice making plates are disposed facing each other approximately vertically sandwiching an evaporation tube configuring a refrigeration system, ice blocks are generated by flow-down supplying ice making water on a surface (ice making surface) of each of the ice making plates cooled by a refrigerant circulatively supplied to the evaporation tube in ice making operation, and the ice blocks are separated by shifting to deicing operation to fall down and released (for example, refer to Patent Document 1). Such a flow-down type ice making machine warms the ice making plates by supplying a hot gas to the evaporation tube in deicing operation and also flowing deicing water at normal temperature down on a back face of the ice making plates, and allows the ice blocks to fall down under its own weight by melting a frozen portion with the ice making surface in the ice blocks.
In the flow-down type ice making machine, a configuration is employed in which a projection projecting outwardly is provided between positions of vertically forming ice blocks on the ice making surface of each ice making plate and such an ice block sliding down along the ice making surface in deicing operation is stranded on the projection, thereby preventing the ice block from not falling down by being caught in an ice block below to prevent the ice blocks to be melted more than necessary. Patent Document 1: Japanese Laid-Open Patent [Kokai] Publication No. 2006-52906